Jen is head on with the Jin is not dead theory. I don't believe it either, he must've jumped at the last moment. Faraday is "near" with the raft full of unknown people, so they can get Jin on the way to the exploded boat.
Good eye there Ele, I completely ignored that flash-forward of Ben. It makes total sense now. If he was slingshotted thru time, that will give him time to prepare his payback.
I was talking about the season finale with my friend-workmate and I said some things to which she replied with a very interesting theory. She said: when Ben moved the island, maybe he didn't move it in space... but in time. If the island moved 1 day, 1 week or 1 month forward that will buy enough time for people to go their way before the island reappears at the same spot.
ps - If it was only a few hours to a day forward, that could give hope to Faraday (and Jin, if he found him) returning to the island. But this is only speculation.